Solvent extraction of oils and acids



June 27, 1 944.

J. D. JENKINS SOLVENTYEXTRACTION OF OILS AND ACIDS Filed May' 13, 1940highly unsaturated or Patented June 27, 1944 I 2,352,546 SOLVENTEXTRACTION OILS AND ACIDS John D.

Jenkins, Forest mus, ra., assigner 'to Pittsburgh Plate Glass County.Pa., a. corporation Company, Allegheny of Pennsylvania Application May1.3, 1940, Serial No. 335,006 11 Claims. (.Cl. 260-419) The presentinvention relates to rening ci glycerides of fatty acids andthe freeacids derived therefrom, and it has particular relation to therefinement by liquid phase extraction with a polar solvent of suchglycerides and acids consisting of components .which substantiallydiffer urated or less actively unsaturate'i` material in which isdissolved a small amount of the solvent.

These two liquid phases may be separated by from each other by reason ofa difference in degree of unsaturation or activity of unsaturation, orin chain length of the molecule.

One object of the invention is to provide a process of removing acomponent from glycerides and free fatty acids of glycerides byextraction with av selective solvent, which process does not produceobjectionable reactions that impair the value of one or more of thecomponents of the material treated.

This and other objects of the invention will be apparent fromconsideration of the following specication and the appended claims.

In copending applications Serial No.` 144,315, now issued'as Patent2,200,390 led May 22, 1937 and 251,340, now issued as Patent 2,200,391tiled January 17, 1939, to Stephen-E. Freeman are disfree acids ofglycerides into components by liquid phase extraction with furfural,furfuryl alcohol and other active or polar solvents, which includevarious activating groups such as OH, COO, NO2, P04, and numerous othergroups. These active solvents are found to have a substantially higherailinity for unsaturated glycerides and acids derived from suchglycerides than for the more saturated or otherwise less activeglycerides or acids. Correspondingly the more actively unsaturatedglycerides Iand free acids thereof exhibit a substantially greatersolubility in the solvents than the more completely saturated glyceridesand acids or the unsaturated glycerides which by reason of thearrangement of groups are less active.

Under the provisions of the foregoing applications, oils and acidsAcorfsisting of mixtures of more completely saturated andless'completelysaturated or actively unsaturated components are treatedwith anactive or polar solvent to dissolve out a fraction enriched inthe more un. saturated'or actively unsaturated componentsl andcorrespondingly to leave a rafnate of oil or acid which is enriched inthe relatively highly saturated components, together with a certain`amount of the active solvent dissolved therein.

The mixture can then'be separated into liquid appropriate means, and bydistillation or other suitable treatment, the solvent may be removedtherefrom, leaving the desired fractions of oils or acids.

Although it was thus possible to separate glycerideoils or the acidsderived therefrominto fract ns according to the degree orthemoleculaarrangement of unsaturation 'the unsaturated fraction did not alwaysexhibit the characteristics desired in it. to the degree that might havebeen expected. VFor example, where the fraction was to be employed as avpaint or varnish vehicle, it was often found that the extracted fractiondried slowly even though its iodine value soV ` closed processes ofseparating glycerides and also phases,lone consisting of the solventandthe fraction richin unsaturates or active unsaturates and the otherconsisting of the more Satwas relatively high. Food products might bediscolored.

It has now been discovered that this peculiar behavior is apparently dueto some obscure chemical reactions within the oil or solvent or possiblybetween the two. It has further been discovered, thatl if anunsaturated'glyceride or the free acids therefrom is extracted with asuitable selective-polar solvent such as furfural, while it is blanketedor covered with an inert gas, such as carbon dioxide, ilue gas, ornitrogen, the tendency is substantially eliminated. From this it may.perhaps, be deduced that the peculiar beto the action of atmosphericoxygen which is blanketed out or excluded by the inert medium coveringthe oil.

In the application of the principles of the invention various methods ofextracting the oil with solvent may be employed. For example, extractionmay be conductedas a simp batch operation by mixing the oil and solvenunder a blanket .of inert gas in a suitable container,

`havior of the extracted oil is in some way duey then allowing theresultant fractions-to separate into liquid layers anddrawing o .thelayers into separate containers for removal of the solvent. However, thepreferred method 'involves countercurrent extraction in columns in whichall -free surfaces of the glycerides or acids ,are protected by ablanket of inert gas. The gas may be almost any inert gas, such, ascarbon dioxide; however, nitrogen or nitrogen containing gases, Vsuch asilue gas, are preferred.

f A suitable embodiment of apparatus for .countercurrent extraction isillustrated in the accom- Danying4 drawing in which the single sure is adiagrammatical or schematic view -oi' a suitable conduit 28 dischargessolvent is the .heavier inlet foi the solventembodiment of apparatus foruse in' practice of the invention.

In the drawing like numerals refer to like parts throughout.

The apparatus as disclosed includes an extraction tower o'r column` IIIwhich may be packed with Raschig rings or Berl saddles, etc.. and may beof substantially any diameter dependent upon the quantity of glyceridesor acids to be passed f therethrough. The height of the columnpreferably is approximately within the range of 30 to 50 feet. However,these limits may be sul) stantially exceeded, if so desired. It also isprovided with a. cover or jacket II,'which, as shown, may be formed inseparate sections, such as I2, I3 and I4, which may be of substantiallyany number dependent upon the gradation of temperature within thelcolumn which it may be desired to maintain. The sections may -besupplied through eaclr section of the jacket individually or to causethe iluidto flow from the outlet of one section to the inlet of theadjacent section as miLv be desired.

Glyceride oil or free acids of glyceride oils may be stored Vin a clodcontainer 2I, which, may be provided with a jacket 22 by means of whichit may be maintained at any desired temperature.

' Oil from the container nows through conduit 22 and is forced bysuitable pump 24 into an intermediate portion of the column III,preferably at a distance of about 12 feet from the bottom of the column.

solvent gradually extracts a fraction which is rich in the more solublecomponent, such as the more unsaturated or actively unsaturatedglycerides and acids, or the glycerides or acids which are more solublevby reason of differences in chain length in the molecule. The lesssoluble components of the oil do not dissolvein the solvent, at leastnot completely but do tend to take up a certain amount of the solvent.In a zone near or slightly above the inlet for the conduit 28 the lesssoluble component or raffinate will collect as a body 36 of insolubleglyceride oil, or' oil acid, which is free of the extract phase andwhich is saturated or substantiallysaturated with solvent and may bedrawn oil througha conduit 31, that leads to suitable apparatus (to belater described) for the separation of the solvent dissolved therein.Inert gas is admitted through conduit 31a to blanket the railinate.

The undissolved solvent with the vextract phase therein ultimatelyseparates out inthe bottom of the column as a distinct layer or fraction39', which may bedrawnoi through a conduit 4I, that extends upwardly asufficient height to admit of hydrostatically balancing of the liquidtherein against the liquid contained in the extraction column I0.

Since the solvent and the oils are of different specific gravity, andsince Eunder varyirm conditions there will be a tendency for therelative amounts thereof in the column III to vary somewhat, itisrdesirable to provide at the upper exl tremity of the conduit 4I asection 42 which can be elevated or lowered to accommodate for thevariations, thus making it possible to assure that the various strata inthe column I0 are approximately at the desired levels. 'I'he upper exftremity of the adjustable section 42 is provided with a head 43', inwhich the pressure may be atmospheric. This head is filled with inertgas through conduit 42a.

Solvent for the extraction may' be stored in ,a container 2l and is fedthrough conduit 2l to a pump 21, connected to conduit 28 in a heaterjacket 2l, having atjone extremity an inlet II for heated fluid such aswater and at the opposite extremity an outlet 22 for the waste fluid. Insome instances it may be desirable to add water or other fluid at leastpartially miscible with the solvent, but immiscible with the material tobe refined, in order to reduce miscibility thereof in the solvent. Suchaddition may be made through conduit 32a. The upper extremity of ofthecolumn Il at a short distance' froml the top thereof. Inert gas may,also. be supplied to container through conduit #2b. v A

It will be apparent that by reason of thedifference inspeciiic gravityof the solvent and the glyceride oil or the acids derived therefrom the'will tend to ilow counter-currently to each other. Assuming that thecomponent it will descend while the undissolved oil will rise. YTherefore, in a zone 33 extending approximately from the down somedistance below the 'inlet for the glyceride oil orthe acids, there willbe a-mixture of countercurrently flowing components. Also, the oil willbe carried by the solvent a certain distance below .the oil inlet. Inthe sone of countercurrent flow of selective solvent and oil or acid itwill be apparentthat there is very intimate contact, and the selectivetwo liquids with respect into the-upper extremity 'I'he solvent chargedwith extract discharges through this head to a conduit 44 leading to theupper extremity of a flash vaporizing column 40, provided with a jacket41 to which steam at a pressure of 20 or 30 pounds per square inch oryother heat exchange mediu'm may be admitted through conduit 48 and fromwhich spent medlum is discharged through conduit 49.. The oil isdelivered into column 4l as a shower or spray that falls into a spraytrap 5I in which the droplets of separated oil, largely freed of thesolvent, are collected. The column 46 preferably 'is maintained underpartial vacuum, e. g. under a pressure of 100 or 300 m. m. Vaporizationof solvent in the column is valmost instantaneous. The solvent vaporspass oil! from the trap through conduit 52 to `a condenser 53, which inturn discharges through conduit 5,4 and pump 58 back to the solventcontainer 2l.

The .extract separated from the vaporlzed sol-l vent in the trap isdischarged through conduit 51 to a surge tank it, having inlet Bl forinert gas. From the latter, it, or any suitable portionthereof, isdischargedthrough conduit llrto stripping apparatus (to be describedlater) for removal of the last traces of the solvent contained therein.A portion of the extract with the small amount of solvent therein isdischarged through conduit 42 to pump which forces it'through conduits 4back'into the column Il at a point preferably below the feed oil inlet,but slightly above the upper limit ofthe separated solvent phasein thelower portion of theicontainer. The concentra,-

:conduit 8l. y Column 1B preferably is packed with an inert ,materialsuch as Raschig rings, Berl saddles or other packing material designedto check the 'discharged into he une 12. The remate cu tion'of the moresoluble component is thus increased in a zone adjacent tosolvent-extract layer and this results in the separation of more oftheless soluble component from the oil so that ultimately an extract isobtained, which isricher in the more soluble component and poorerin theless soluble component, than would otherwise be obtained. Substantiallyany ratio of the extract, for example 10 to 90% of the extract may berecycled.

As previously stated the inlet for the recycled oil is slightly abovethe level of the separatedl solvent and preferably it is at suchdistance below the level of the inlet for theA oil that the recycledoil, as it passes upwardly through the solvent, will reach approximatelythe same composition as the feed oil from the container 22. Assumingthat furfural is employed as the selective solvent the distance betweenthe inlets of the feed oil and the recycled oil'may be approximately l2feet. The distance between the inlets for the feed oil and the solventmay vary over a substantial range, but preferably is about l to 35 feet.

1f preferred, separation of the extract from the A solvent may be eectedby addition of water, e. g. 3 to 15% of water or other non-solvent. Thevaporizer 46 may then be eliminated or may be bypassed by conduit 65interconnecting conduit 44 and conduit 5l. Separation of the extract maybe eiected in the surge tank 58 by addition of .water through conduit65a.

The apparatus for removing the dissolved solvent from the rainateincludesla vaporizer column 66 into the upper extremity of lwhich theconduit 3l discharges the railinate as av spray. 'Ihe column is providedwith a heating packet 61, which is supplied with steam or. other heatediiuid by means of conduit 88 and the spent iluid is discharged from thejacket through y'conduit 69. The pressure within the column 66 like thatin column 46 is subatmospheric-e. g., about 100 to 300 m. m. of mercuryand Aevaporation of the most of the solvent is almost instantaneous. -At

now freed of solvent is discharged through conyduit 84 at the bottom ofthe column and is passed to storage or is passed on for furthertreatment,

for example, for an additional extraction in further stages ofapparatus. Such stages obviously may assume substantially th form of theapparatus herein disclosed and by such treatment it is possible toremove an additional fraction or fractions of more soluble componentfrom the rainate. y

The conduit 6l carrying the more soluble or extract components of theglyceride oil or the its lower extremity the column discharges into aconventional Spray trap lli, in which the droplets of railinate fromwhich much of the dissolved solventhas been evaporated are collected.

The solvent freed of raiiinate and in vapor acids thereof, namely themore unsaturated components, is disharged into a second stripping vcolumn 86 substantially'corresponding in construction tothe column 'i6and having a jacket 81 for steam or other iluid as previously vdescribedin connection with the column 16.' The column is also packed asindicated at `88 and is supplied with steam or inert gas through conduit09. The steam or gas charged with solvent discharges fromthe upperextremityoifV the column through conduit 9i, which also dischargesintothe vapor line 13 and passes on to suitable apparatus for separation' ofthe solvent from the water vapors or gas. 'Ihe component of the oilwhich initially is dissolved in the solvent and which is liberated inthe column 88 is discharged from the bottom of the latter through aconduit S2, is either passed to storage or is subjected to furthertreatment, for exaniple, to further fractionation in additional stagesof apparatus in order more completely to separate out any saturated orless soluble 4components which may be carried therein. In this way afraction which is very rich in unsaturates. or other component, which isselectively soluble in the solvent employed, may be obtained.

In the practice of the present invention 'substantially any of thelselective solvents disclosed glycol diacetate, ethyl oxylate, methylcellosolve state is discharged through'a conduit 12, to a line 73leading to a condenser and source of vacuum (not shown). The ramnate,separated from the vapors in the trap 1| and still containing -somesolvent, isdischarged through conduit i4 into the upper extremity of astrippingv column 16, which column is provided with a -jacket Ilsupplied with steam or other heated nuid through conduits 18, having aconnection to a supply line 19. Where steam is employed the pressure is.preferably about lbs. per square inch corresponding to about 280 F'.The spent iluid is discharged from the bottom of the jacket throughdescent of the oil and to cause it to be spread out into thin' lmspresenting large surfaces.

Steam or other distilling medium is introduced charged with solventthrough conduit 83 and is 76g acetate and others. 'Ihe ratio of solventto oil may vary over a broad range extending for example of 1 to 1 allthe way to 10 to 1.

i The solvent system may include a solvent iml miscible therewith, suchas a paraillnic".hydro carbon having la boiling point above thatI ofoperation of the extraction system. Isooctane is va good example of suchsolvent. It may lbe-used in a range of from about 1/2 to 5 parts foreach part of polar solvent. It often asists in separating the lessactive componentsv oi' the oil or acids by dissolving them out ofthe'polar solvent.

Among'the glyceride oils that may be fractionl ated are included bodiedor unbodied linseed oil.

marineoilasuch as -menhademsardine and whale oils, soya bean oil,perilla oil, Vcottonseed oil, com oil, sunflower oil, peanut oil, oliveoil, lard, tallow and the like. These oils comprise mixtures oi'glycerides of varying degrees of satu-`l ration andfractionation thereofis eifected-by the selective solvent by reason of the'higher de.

gree of solubility of 'the more unsaturated components'in the selectivesolvent.l The oils and free fatty acids may be deaerated priorto-extraction, by heating them to C. or thereabout andsimultaneouslyqsubjecting them-to vacuuml-ortoblowingwithnitrogenorotherinertgasyThe'oilsmay-be rawoilsormaybealkallrelined, or may be reilned by other methods. 'I'heymmalso, be bodied or unbodied.

. It'has also been found that certain of the oils. suchas ,palm oil andcoconut oil, which include intheirqcompositions glycerides of fattyacids of varying chain length can similarly be separated intofractions,l because of the greater solubility ofv the short chain acidglyeerides in the selective solvent. For example, coconut oil whichcomprises essentially mixtures o fglycerides of straight chainaliphaticacids of a chain lensth from 6 or 8 up to 1 8 or more maybeseparaied into fractions which are greatly enriched in speciilcglycerides.

`*It is of course obvious that the apparatus and process as hereindisclosed is-also applicable to the fractionation .of mixtures ofrelatively saturated and relatively unsaturated fatty acids derived fromthe oils herein disclosed.`

Almost any inert gas, such as carbon dioxide, carbon monoxide, nitrogen,or a nitrogen containing sas such as flue gas may be employed as Thegases may be preliminarily dried in order toprevent hydrolysis of thesolvent in the system.' If the solvent does nottendto hydrolyze,suchsdrying is'- not usually necessax'yf, The inert gases not; onlyprevent objiectionable chemical reactions;4 but they also reduce nrehazards in the system, especially where immiscible hydrocarbons-arepresent. They also help to reduce objectionable discoloration of thefractions ob- `Under,some conditions it may be possible to get'substantially the same effects-as obtained by blanketing the liquidsin-the apparatusby-so constructing ,it as to exclude all contact of the.iiuidswith air.

The extracted oils as obtained from linseed, soya bean. marine oils,perilla oil and others containing substantial amounts of slycelldes su sceptible of air drying are excellently adapted for use-as drying oils inthe fabrication of paints and tively more soluble in a furane compound.-which process comprises providing a mixture of a furane compound and thematerial under a blanket oi inert gas and thenseparating the mixture,into liquid phases, one comprising the furane'compound saturated withthe more soluble component and the other comprising the less solublecomponent saturated with the furane-compound.

-2. A process as defined in claim l in which the furane compound andmixture to be separated into components are tlowed countercurrently in atower and the Iliquid phases are collected respectively at the top andbottom of the column, separated by the vintervening mixture ofcountercurrently flowing materials.

3. A process as'deilned in claim 1 in which the furane compoundisfurfural and the inert gas consists mainly of nitrosen.

4. A process of separating into components a mixture selected from aclass consisting of a mixture of a plurality oi' glycerides and a.mixture of a, plurality of fatty acids derived from said glycerides,said mixtures each including component which is relatively diilicultlysoluble and a component which is relatively more soluble in a furanecompound. which process comprises countercurrently i'lowing a furanecompound and theL material to be separated into components in a tower,collecting as separate liquid phases a soluti t n of the furane compoundin the less soluble com s 2- t and a solution of the more solublecomponent the furane compound drawing off the |latter phase through 'astand-pipe balancing the liquids in the columns, the material in thecolumn and the stand-pipe under a blanket of inert gas.

5. A process of separating into fractions a material selected from aclass consisting of Glycerlde oils and free acids of said oils, onefraction being of a relatively high degree of saturation and a secondfraction being of a relatively high degree of unsaturation, whichprocess comprises contacting the mixture with a furane compound solventfor the unsatmated component which has relawhich comprises the firstcomponent saturated By application of the extraction process extractedoil having good drying properties and smiiietly free of obieconble mme*auch as free acids, anti-oxidants break producing constituegtsand thelike canA be obtained without ecting' the oil to severe treatment withacid f In the fabrication of paints and varnishe'sthe Vconventionalpigments, colors, thinners 'and the like are added as with conventionaldrying oils. For example, titanium oxide, lithopone` and other pigmentsmay be added in amounts of 5 to 90%. Turpentine or any other volatilethinner may be also added in an amount of 5 to 90%. more or less. basedupon weight.

The forms of the inv tionherein disclosed constitute only a part o thepossible applications ofthe invention. It will be apparent that numerousmodifications can be made therein without departure from the spirit ofthe invention or the scope of the claims.

i. A process of separating into components aj mixture selected from aclass consisting of a* of a plurality of glycerldes and a mixtureconsisting of, `a plurality of 'fatty acids" derived from saidglycerides, said mixture including a component which -is relativelydiiiicultly soluble and a component which isl relawith the furanecompound and the second of which isv the furane compound saturated withthe second component, said extraction being effected in the absence ofoxygen.

6. A process oi'. separating into fractions a material selected froma'class consisting of glyceride oils and free4 acids of said oils, onefraction being of a relatively high degree of saturation and a secondfraction :being off-a relatively high'degree removing the furfuraltherefrom and recycling the furfural for extraction of additionalmixture, the furfural and the mixture being at all times excluded fromcontact with oxygen.

7. A process of separating into fractions a ma-V terial selected from aclass consisting of glyeride oils and freeacid'sofsaid oils, onefraction being' of a relatively highrliegree of saturation and a secondfractionbeing of a relatively high degree o funsaturatign. which.process comprises contactingthe. mixture with f urfural to form twoliquid, phases, one comprising the relatively saturated fraction havingsome tui-tural dissolved 2,852,546 therein, the other comprisingfurfural in which is dissolved a relatively large amount of theunsaturated i'raction, separating the two phases. removing the furfuraltherefrom and recycling the furfural for extraction of additionalmixture, the iurfural and the mixture being at all times excluded fromcontact with oxygen, by blanketing them with an inert gas.

8. A process of separating into fractions a matei-iai selected from aclass consisting of glyceride oils and free acids of said oils, onefraction being of a relatively high degree of saturation and a secondtraction being of a relatively high degree of unsaturatlon, whichprocess comprises contacting the mixture with iurfural 'to form twoliquid phases, one comprising the relatively satuis dissolved erelatively :me amount of the un.

saturated fraction, separating the two phases, removingthe mrturaltherefrom' and recycling the furi'ural for .extraction oi additionalmixture, the furiural and the mixture being at all times excluded fromcontact with oxygen. by blanketing them with a gas consisting mainly oftree nitrogen.

9. A process as deiined in claim 5 in which the solvent is iuriural andthe material treated is rated fraction having some furfural dissolvedtherein, the other comprising furfural in which from a class consistingoi' soya bean oil, cottonseed oil, coconut oil, and linseed oil. 10. Aprocess as defined in claim 1 in which th solvent is further admixedwith a hydrocarbon immiscible therewith.

11. A process as dened in claim l in which the material treated ispreliminarily deaerated.

JoHN D. JENKINS.

